The pretty obvious reason in my opinion: Ethereum's fees have been quite high for a while, and Binance Smart Chain(BSC)'s fees are drastically lower. And yes, BSC is like magnitudes more centralized than Ethereum, but it comes to show how a lot of people don't care that much if a certain project is decentralization or not as long as they can make their bets on certain tokens.
I totally agree with your opinion. even I myself liked eth very much because of their Decentralized nature all the cool features. but this insanse gas fee. just made me move to alternative sources even if they are centralized and do not give that much freedom as eth.
I think Eth Dev better solve this problem.
Binace reached to 3rd top currency. if eth goes like that there is very much possibility that binance will overtake eth one day.